This invention relates generally to gas turbine engines, and more particularly to heat exchangers used with gas turbine engines.
At least one known gas turbine engine uses a heat exchanger, generally referred to as a recuperator, to facilitate reducing specific fuel consumption. More specifically, pressurized air from the compressor section of the gas turbine engine is channeled from the gas turbine engine, and through the heat exchanger, such that the hot exhaust gases of the engine raise the operating temperature of the pressurized air prior to it being supplied into the combustor.
Known heat exchanger assemblies are positioned between the gas turbine engine exhaust gas box and the exhaust stack. At least some known heat exchanger assemblies include a pair of heat exchangers coupled in a parallel spaced relationship such that a space known as a bypass duct is defined therebetween. The bypass duct is closable by a butterfly valve. However, since known heat exchangers are typically physically large and rectangular-shaped, such heat exchangers are mounted externally to the gas turbine engine. Accordingly, the compressor discharge air and the engine exhaust gas is routed to and from the heat exchangers through a ducting which couples the heat exchangers to the gas turbine engine. As a result, known heat exchanger assemblies occupy a relatively large volume which is often larger than a volume occupied by the gas turbine engine itself. The resulting large and irregular heat exchanger assembly, coupled with the added weight and cost of the heat exchanger and ducting, generally makes regenerative engine systems unfeasible for aircraft applications.
In addition, although recuperated engines generally achieve a better low power specific fuel consumption than other known gas turbine engines, when such engines are operated with a heat exchanger assembly and at a higher operating power, gas-side total pressure losses of the hot exhaust gas stream may be relatively high through the exhaust system heat exchanger. The increased gas-side pressure losses caused by the heat exchanger assembly may result in an increased specific fuel consumption. Moreover, since the size of the heat exchanger is generally desired to be as small as possible, less space is available for a bypass system, which may result in high exhaust total pressure losses during high-power engine operating conditions.